The purpose of these investigations is to identify pharmacologic agents that will increase tensile strength of arterial and valvular connective tissue in man. Using the domesticated white turkey, in which intrinsic weakness of the abdominal aorta leads to spontaneous dissecting aneurypms and lathyrogens increase the incidence of aneurysms, we find a blocking of lathyrogenic action by drugs that interfere with adrenegic receptors. Propranolol, a beta-adrenegic receptor antagonist, was shown over the past year to have a dose-related effect in increasing tensile strength of the turkey abdominal aorta. Propranolol appears to enhance the lysyl oxidase system (the key enzyme in the production of the reactive aldehydes that form elastin and collagen cross-links) as evidenced by increased amounts of borohydride-reducible hydroxynorleucine and the cross-links merodesmosine and lysinonorleucine in the abdominal aorta of drug-treated turkeys. Propranolol had no effect on the amino acid composition or on the density of isodesmosine and desmosine of the isolated elastin. When propranolol is given in combination with androgenic hormone, tensile strength of the tissues is increased, and amounts of borohydride-reducible elastin and collagen cross-links are lowered while levels of non-reducible elastin cross-links (isodesmosine and desmosine) are increased. These results are providing direction for an ultimately useful therapeutic regimen for a variety of here-to-fore untreatable human ailments. For purposes of drug treatment of humans, clinical means must be developed for assessing pharmacologic action. We have developed techniques for measuring the amounts of isodesmosine and desmosine in human urine. Using a multi-step procedure (acetone precipitation yields molecular sieving yields borohydride reduction yields acid hydrolysis yields paper chromatography yields amino acid analysis with 5-buffer system), the demosines were isolated and chemically characterized. Preliminary results reveal lower urinary desmosines in young patients with Marfan's Syndrome.